Nonfluoroscopic 3D Image Guidance System Reduces Navigation Times Through Five 3D-Printed Iliofemoral Vascular Phantoms.

PURPOSE: To assess the potential adjunctive role of a 3D electromagnetic (EM) navigational system for use in above-knee vessels afflicted with peripheral artery disease (PAD). Peripheral artery disease can be challenging to operators encountering significant vessel tortuosity, calcium, and stenoses, which may require prolonged procedure times and excessive use of nephrotoxic iodinated contrast when performed with conventional fluoroscopy. MATERIALS AND METHODS: Following appropriate ethical oversight, five 3D-printed bench phantoms modeling tortuous calcified PAD were created based on source CTA (computed tomography angiography) data sets from real patients. Investigational software was developed based on a commercially available aortic EM navigation platform (Intraoperative Positioning System [IOPS]; Centerline Biomedical, Inc., Cleveland, Ohio), with patient-specific structural maps of vessel lumens and calcification. Using a sensorized prototype 6 French (Fr) catheter and 0.035" guidewire, 15 interventionalists traversed each phantom using the EM platform as well as 2D simulated fluoroscopy-like image guidance and the times were recorded. Participants completed a 10-item standard system usability scale (SUS) questionnaire (score 1-5, 5=strongly agree) evaluating system usability and user satisfaction. Navigation times and SUS scores were compared with a 1-tailed statistical t test. RESULTS: Participants demonstrated a statistically significant reduction in navigation times using EM guidance, performing 0.7 minutes (42 seconds) faster on average (P < .001), corresponding to a 25% average relative reduction. Participants reported sufficiently high levels of usability satisfaction, with a mean SUS score of 4.29 (P < .001), exceeding the acceptance criterion (score ≥3.5). CONCLUSION: This preclinical phantom study highlights the future potential of Centerline Biomedical's EM navigation technology as a possible adjunct to fluoroscopy for highly precise visualization and navigation of PAD-afflicted vasculature. CLINICAL IMPACT: This preclinical proof-of-concept study highlights the feasibility of EM navigation not only for branch vessel cannulation, but also for inline navigation of peripheral vessels afflicted with calcified plaques via benchtop iliofemoral phantom simulations. The navigation platform studied addresses the need for improvements in EM technology through modelling algorithms that facilitate 3D visualization of calcified plaque in any projection in real time, in addition to sensorization of both catheter and guidewire in a compact 6Fr system.

Branched Endovascular Thoracoabdominal Aneurysm Repair Under Electromagnetic Guidance in an in Vitro Model.

PURPOSE: We report a new approach to perform endovascular treatment of thoracoabdominal aneurysms under electromagnetic navigation guidance using a modified system (IOPS; Centerline Biomedical, Inc., Cleveland, OH, USA) and a modified branched endograft (E-nside TAAA Multibranch Stent Graft System; Artivion Inc., Kennesaw, GA, USA). CASE REPORT: We performed this case in an aortic in vitro model made from transparent polyurethane in our research hybrid room (Discovery IGS 730; GE HealthCare, Chicago, IL, USA). While the implantation of this device typically involves several challenging steps, including precise endograft implantation, snaring of preloaded guide wires, and cannulation of target visceral arteries, all were successfully performed using electromagnetic navigation guidance. CONCLUSION: Our preliminary experience suggests that endograft implantation under electromagnetic navigation guidance in an integrated hybrid operating room is an innovative option to address technical challenges and reduce patient and operator radiation exposure associated with complex endovascular surgery. CLINICAL IMPACT: Most steps of a branched endografting procedure can be performed without X-Ray exposure when using electromagnetic navigation guidance and a modified branched endograft.

Successful endovascular treatment of severe chronic mesenteric ischemia facilitated by intraoperative positioning system image guidance.

We report our initial experience using the intraoperative positioning system (IOPS), a novel endovascular navigation system that does not require contrast or radiation, in the treatment of chronic mesenteric ischemia (CMI). We used IOPS to help treat three of four consecutive patients with CMI. Technical problems prevented successful use in one patient. For the patients for whom IOPS was used effectively, catheterization of the mesenteric artery was accomplished more quickly than for the patient for whom IOPS was not effective. Our experience has shown that IOPS can be safely and effectively used for CMI and can reduce the contrast load and radiation dose.

Three-Dimensional Holographic Guidance, Navigation, and Control (3D-GNC) for Endograft Positioning in Porcine Aorta: Feasibility Comparison With 2-Dimensional X-Ray Fluoroscopy.

OBJECTIVES: Intraprocedural deployment of endovascular devices during complex aortic repair with 2-dimensional (2D) x-ray fluoroscopic guidance poses challenges in terms of accurate delivery system positioning and increased risk of x-ray radiation exposure with prolonged fluoroscopy times, particularly in unfavorable anatomy. The objective of this study was to assess feasibility of using an augmented reality (AR) system to position and orient a modified aortic endograft delivery system in comparison with standard fluoroscopy. MATERIALS AND METHODS: The 3-dimensional guidance, navigation, and control (3D-GNC) prototype system was developed for eventual integration with the Intra-Operative Positioning System (IOPS, Centerline Biomedical, Cleveland, OH) to project spatially registered 3D holographic representations of the subject-specific aorta for intraoperative guidance and coupled with an electromagnetically (EM) tracked delivery system for intravascular navigation. Numerical feedback for controlling the endograft landing zone distance and ostial alignment was holographically projected on the operative field. Visualization of the holograms was provided via a commercially available AR headset. A Zenith Spiral-Z AAA limb stent-graft was modified with a scallop, 6 degree-of-freedom EM sensor for tracking, and radiopaque markers for fluoroscopic visualization. In vivo, 10 interventionalists independently positioned and oriented the delivery system to the ostia of renal or visceral branch vessels in anesthetized swine via open femoral artery access using 3D-GNC and standard fluoroscopic guidance. Procedure time, fluoroscopy time, cumulative air kerma, and contrast material volume were recorded for each technique. Positioning and orientation accuracy was determined by measuring the target landing-zone distance error (δLZE) and the scallop-ostium angular alignment error (θSOE) using contrast-enhanced cone beam computed tomography imaging after each positioning for each technique. Mean, standard deviation, and standard error are reported for the performance variables, and Student's t tests were used to evaluate statistically significant differences in performance mean values of 3D-GNC and fluoroscopy. RESULTS: Technical success for the use of 3D-GNC to orient and position the endovascular device at each renal-visceral branch ostium was 100%. 3D-GNC resulted in 56% decrease in procedure time in comparison with standard fluoroscopic guidance (p<0.001). The 3D-GNC system was used without fluoroscopy or contrast-dye administration. Positioning accuracy was comparable for both techniques (p=0.86), while overall orientation accuracy was improved with the 3D-GNC system by 41.5% (p=0.008). CONCLUSIONS: The holographic 3D-GNC system demonstrated improved accuracy of aortic stent-graft positioning with significant reductions in fluoroscopy time, contrast-dye administration, and procedure time.

Impact of alterations in target vessel curvature on branch durability after endovascular repair of thoracoabdominal aortic aneurysms.

OBJECTIVE: The aim of this study was to evaluate curvature and its effect on the durability of visceral and renal branches in patients undergoing endovascular repair of thoracoabdominal aortic aneurysms (TAAAs) with fenestrated/branched endovascular aneurysm repair (F/B-EVAR). METHODS: Quantitative branch vessel curvature assessment on branches arising from reinforced fenestrations was performed for 168 patients undergoing F/B-EVAR for type II and type III TAAAs. Preoperative and postoperative centerline coordinates were obtained using iNtuition (TeraRecon, Foster City, Calif) and exported into MATLAB (The MathWorks, Inc, Natick, Mass) based on thin-slice computed tomography imaging. Spline interpolation was applied to the centerline coordinates and resampled at 100 equally spaced points, and curvature calculations (κ, mm(-1)) were applied. Global and maximal curvatures for each of the target vessels were measured and categorized by severity. Categories for curvature were 0 to 0.05 mm(-1) (low), 0.05 to 0.1 mm(-1) (medium), 0.1 to 0.15 mm(-1) (high), and >0.15 mm(-1) (extreme) for global curvature and 0 to 0.2 mm(-1), 0.2 to 0.4 mm(-1), 0.4 to 0.6 mm(-1), and >0.6 mm(-1), respectively, for maximum curvature. Curvature variances were assessed for an association with vessel patency and need for reintervention. RESULTS: There were 558 vessels that underwent analysis based on repairs involving 650 vessels, whereby 92 vessels were excluded as they were treated with an external helical branch (58 celiac arteries and 34 superior mesenteric arteries). There was a significant difference found before and after F/B-EVAR for the global celiac artery curvature (median difference, -0.01; P < .001), global left renal artery curvature (median, -0.01; P = .014), maximum left renal artery curvature (median, 0.05; P < .001), and maximum right renal artery curvature (median, 0.03; P = .009). Maximum artery curvature was found to have shifted distally in all vessels postoperatively; 37 adverse events (AEs) were observed in 30 patients (6 branched occlusions and 31 reinterventions [24 type III endoleaks, 5 vessel stenoses, and 2 vessel occlusions]). The majority of AEs (>70%) occurred within the range of low to medium curvature. Univariate analysis found gender to be a dependent variable associated with high (maximum) preoperative curvature (odds ratio, 0.395; P = .02). The use of self-expanding stents (vs balloon-expandable stents alone) in vessels with high preoperative curvature (>0.6 mm(-1)) was significant in the right renal artery (P = .044). CONCLUSIONS: This study did not show a significant relationship between the severity of artery curvature or changes in curvature and AEs found for visceral or renal branches after F/B-EVAR for extensive TAAA. Surprisingly, the majority of AEs occurred in low- and medium-curved vessels. This study is limited in that it does not take into account other factors that may affect AEs, like motion, which would be valuable in future studies.

Cycle testing of the MagScrew total artificial heart external battery pack: update I.

MagScrew total artificial heart (TAH) external battery pack (EBP) cycle bench testing continued over a period of 18 months using two fresh Wilson Greatbatch lithium ion EBPs during continuous charge and discharge cycles under a simulated TAH system current requirement. The same electronic load developed for our initial testing was used to simulate the MagScrew current waveforms typically observed during nominal operation. The current load profiles for this test were modified from the ones previously described and applied to the EBP under test during a voltage-defined discharge cycle. The test ended when EBP#2 reached end of life at 1450 cycles. At that point, EBP#1 remained healthy with a capacity of 175 min until full discharge. Performance of EBP#2 was still within expected ranges. Performance of EBP#1 exceeded expectations. These differences are probably caused by slight manufacturing changes. More tests will provide additional data to define a statistical distribution to better characterize EBP performance. In conclusion, endurance performance of the EBP remained satisfactory.

Automated vascular geometric analysis of aortic aneurysms.

An automated geometric analysis procedure uses volumetric computerized tomography scan data to produce a fully defined analytical model of the patient's arterial geometry with minimal user interaction. This model can be a powerful tool for surgery planning and stent design in addition to providing a basis for computational simulations.

Mathematical analysis of DICOM CT datasets: can endograft sizing be automated for complex anatomy?

OBJECTIVES: To validate the use of a novel mathematical algorithm applied to digital imaging and communication in medicine (DICOM) computed tomography (CT) data to automate the generation of complex endovascular graft planning. METHODS: An algorithm was developed enabling the creation of patient-specific mathematical model based upon DICOM CT data to allow for detailed efficient geometric analysis with repeatable results. This algorithm was applied to high resolution DICOM CT datasets of 15 patients, selected at random from 350 patients with aneurysms involving the visceral arteries. The longitudinal and rotational relationships of the visceral vessels were determined by the algorithm. For comparison purposes, the same measurements were acquired manually using centerline of flow software by a blinded investigator. The distance between the renal arteries, and location of the renal origins calculated with each method were then compared. RESULTS: Automated results were readily created for all 15 randomly selected patients. The measured versus calculated mean inter-renal artery distances were exceptionally close, differing by a mean of only 1.3 mm with a maximal range of 3.0 mm. The rotational position of the renal origins differed by only 10.5 degrees of arc (21 clock-face minutes) on average and by 32.5 degrees in the worst case. CONCLUSIONS: The generation of an automated mathematical model to represent complex aortic geometry is feasible and reproducible in the context of high-resolution CT data. This process has been validated in 15 patients, where results corresponded with manual measurements that were used to successfully implant customized devices that accommodate the imaged vessels. Additional attributes include the expression of the 3D aorta in a compact form (on the order of kilobytes) for purposes of data storage, transfer, and other manipulations. CLINICAL RELEVANCE: The construct of mathematical representation of patient specific anatomy from CT data is both feasible and applicable, allowing for automated endograft device design even in the setting of markedly tortuous anatomy where the repair must incorporate major aortic branches. The process has been validated in 15 patients, where results corresponded with manual measurements that were used to successfully implant customized devices that accommodate the imaged vessels. The application of this technology must now be studied in a prospective manner and incorporated into a system users may readily apply to patients undergoing evaluation. Additional attributes of a mathematical representation of the arterial tree include the 3D expression from a very compact set of parameters (on the order of kilobytes) for purposes of data storage, transfer, and other manipulations.